(1) Field of the Invention
This invention pertains to the field of motorcycle engines. More particularly, this invention pertains to the configuration of crankcase ventilation passageways within motorcycle engine cam covers.
(2) Background
Motorcycle engines often comprise a cam cover that, in addition to supporting the crankshaft and camshaft, create a fluid passageway for venting crankcase gases. In general, each particular model of motorcycle engine is often provided with a particular cam cover by the original equipment manufacturer of the motorcycle.
This invention pertains to a specific type of cam cover of the type that includes a camshaft support, a crankshaft support, and a fluid passageway for venting the crankcase. More specifically, this invention pertains to such a cam cover comprising a fluid inlet opening and a fluid outlet opening that are connected by the fluid passageway and that are positioned on opposite sides of a plane that includes the camshaft axis and the crankshaft axis. In such a cam cover, it is common for the fluid passageway to comprise a tube that extends from the fluid outlet opening toward the fluid inlet opening and that passes between the camshaft support and the crankshaft support. Due to the relatively close spacing of the camshaft support and the crankshaft support, the tube is typically relatively small in cross-sectional area.
The purpose of the fluid passageway is to allow venting of the crankcase so as to prevent pressure buildup resulting from gaseous fluids escaping past the piston rings. Within the crankcase, such gases are turbulent and oil becomes mixed with and suspended by these gases. Thus, it's desirable to provided some means for separating suspended oil from the gas being vented in an effort to reduce pollution and reduce oil buildup on external surfaces of motorcycles. To this end, most cam covers having such fluid passageways comprise some form of settling chamber or region that is adapted and configured to slow the fluid flow prior to being discharged out of the fluid outlet port. Such settling chambers allow oil suspended in the gaseous fluid to fall out of suspension and drain back into the crankcase.
Cam covers of the particular type described above generally have a small settling chamber near their fluid inlet opening. However, the fluid flow rate through the majority of the fluid passageway, which includes the tube and the fluid outlet opening, is relatively high due to the small cross-sectional areas of the tube and the fluid outlet opening. Thus, only a small portion of the entire fluid passageway facilitates the removal of oil from the fluid being discharged. As a result, at least some oil is invariably discharged from the fluid outlet opening of the cam cover.